The present invention relates to a transportation apparatus in which first and second linkages are coupled to each other to linearly transport an object such as a wafer, and a tension adjustment method of a belt in the transportation apparatus.
For example, there is a known transportation apparatus in Patent Document 1. The transportation apparatus for linearly transporting the object includes a first linkage in which base ends of a pair of first links which have the same length with each other are pivotably coupled to a fixed table through a pair of first coupling shafts, and tip ends of the pair of first links are pivotably coupled to a pair of intermediate shafts which are fixed to a pair of intermediate tables; a second linkage in which base ends of a pair of second links which have the same length with the first links are pivotably coupled to the pair of intermediate shafts, and tip ends of the pair of first links are pivotably coupled to an object installation table through a pair of second coupling shafts; a transmission unit provided in the intermediate table and operable to transmit torque between the first and second links constituting the first and second linkages in both forward and backward directions; and a driving unit provided in the fixed table and operable to drive one of the pair of first links constituting the first linkage to rotate. In the transmission unit, one pulley of a pair of pulleys rotatably supported at the outside of the pair of intermediate shafts is integrally coupled to one of the pair of first links constituting the first linkage, and the other pulley is integrally coupled to one of the pair of second links constituting the second linkage. At this time, the upper and lower belts are partially wound around the pulleys in opposite directions with each other and both ends of the belts are fixed to the pulleys so as to transmit the torque between the pair of pulleys in both forward and backward directions. When the driving unit drives one of the first links of the first linkage to rotate in the forward and backward directions, a driving force is transmitted between a predetermined first and second links constituting the first and second linkages in the transmission unit part. Accordingly, the object installation table disposed at one end of the bottom side of an isosceles triangle formed by the first and second linkages is moved in a straight line shape in the forward and backward directions. In this way, the transportation apparatus linearly transports an object such as a wafer.
At this time, since the transmission unit has a configuration in which the upper and lower belts are partially wound around the pulleys in opposite directions with each other and both ends of the belts are fixed to the pulleys so as to transmit the torque between the pair of pulleys in both forward and backward directions, when the pulleys are allowed to rotate in a predetermined direction to apply tension to one belt in the state where the belts are partially suspended and attached to the pulleys by applying tension thereto, the other belt is loosened so that tension thereof becomes small. As a result, a problem arises in that the tension adjustment of the pair of belts is difficult. Additionally, when tensions of the pair of belts are not appropriate, acceleration abruptly acts on the transported object supported on the object installation table and the transported object deviates from a predetermined position. As a result, a problem arises in that a movement placement of the object is difficult in the subsequent process.    Patent Document 1: Japanese Patent Publication No. 4-331090A